Sed & Awk

sed & awkdescribes two text processing programs that are mainstays of the UNIX programmer's toolbox.sedis a "stream editor" for editing streams of text that might be too large to edit as a single file, or that might be generated on the fly as part of a larger data processing step. The most common operation done withsedis substitution, replacing one block of text with another.awkis a complete programming language. Unlike many conventional languages,awkis "data driven" -- you specify what kind of data you are interested in and the operations to be performed when that data is found.awkdoes many things for you, including automatically opening and closing data files, reading records, breaking the records up into fields, and counting the records. Whileawkprovides the features of most conventional programming languages, it also includes some unconventional features, such as extended regular expression matching and associative arrays.sed & awkdescribes both programs in detail and includes a chapter of examplesedandawkscripts.This edition covers features ofsedandawkthat are mandated by the POSIX standard. This most notably affectsawk, where POSIX standardized a new variable, CONVFMT, and new functions,toupper() andtolower(). The CONVFMT variable specifies the conversion format to use when converting numbers to strings (awkused to use OFMT for this purpose). Thetoupper() andtolower() functions each take a (presumably mixed case) string argument and return a new version of the string with all letters translated to the corresponding case.In addition, this edition covers GNUsed, newly available since the first edition. It also updates the first edition coverage of Bell Labsnawkand GNUawk(gawk), coversmawk, an additional freely available implementation ofawk, and briefly discusses three commercial versions ofawk, MKSawk, Thompson Automationawk(tawk), and Videosoft (VSAwk).